/*
 * Copyright (C) 2017 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.gapid.util;

import java.util.Objects;

/**
 * Contains a mutable reference.
 */
public class ObjectStore<T> {
  private T value;

  private ObjectStore() {
  }

  public static <T> ObjectStore<T> create() {
    return new ObjectStore<T>();
  }

  public boolean update(T newValue) {
    if (is(newValue)) {
      return false;
    }
    value = newValue;
    return true;
  }

  /**
   * Same as {@link #update(Object)}, but ignores passed null values.
   */
  public boolean updateIfNotNull(T newValue) {
    return newValue != null && update(newValue);
  }

  public T get() {
    return value;
  }

  public boolean is(T otherValue) {
    return Objects.equals(value, otherValue);
  }
}
